Control system of marine steam power plant



1967 YASUO TAKEDA ETAL 3,295,320

CONTROL SYSTEM OF MARINE STEAM POWER PLANT 5 Sheets-Sheet 1 Filed Aug. 14, 1964 wQmDOm mw om QEFOMJM wEmEE YASUO TAKEDA! HIROYUKI suzum,

MASAO SHIMIZU ATTORNEYS United States Patent 3,295,320 CONTROL SYSTEM OF MARKNE STEAM PQWER PLANT Yasuo Takeda, Hiroyuki, duzuki, and Masao Shimizu, Kobe-shi, Japan, assignors to Kawasaki .lukogko gflbushiki Keisha, Kobe-shi, Japan, a corporation of apan Filed Aug. 14, 1964, Ser. No. 339,593 Claims priority, application Japan, Aug. 15, 1963, 38/43,211 3 Claims. (Cl. 66-105) The present invention relates to a marine steam power plant, more particularly to a control system for a marine steam power plant wherein ahead and astern running of a turbine is controlled by operating a single handle for maneuvering the steam turbine, the amount of steam and fuel which is supplied to a steam turbine and a boiler respectively will be directly controlled simultaneously and the pressure of the boiler is controlled secondarily by means of an automatic boiler pressure control system.

In a known prior art control system of this kind, when an operator actuates a maneuvering handle in for the turbine to the ahead position or astern position, an ahead maneuvering valve 11 or an astern maneuvering valve 12 will be opened in response to a command of the operator, an ahead steam turbine 13 or an astern turbine 14 will be turned at a predetermined load by a steam supplied from a boiler 15 and will actuate a propeller 16 to propel the ship in the appropriate direction. The amount of steam supplied from the boiler 15 through a main steam pipe 17 to the ahead turbine 13 or the astern turbine 14 will vary dependent upon a degree of movement of the maneuvering handle for the turbine and will cause a steam pressure at an outlet of the steam superheater 18, which is provided in the boiler in a subsequent relation thereto, to vary accordingly. A measured value of the varying steam pressure from the steam pressure sensor will be forwarded to an automatic combusion control system 19, which will be referred to as an ACC system hereinafter, in the form of signal through an electric circuit 20. The ACC system 19 will adjust a degree of opening of a fuel oil valve 21 according to the signal received through the signal wire 22 and thereby regulate the amount of the fuel supplied to a burner 23 from a fuel oil service pump 24 and will also control the degree of opening of the air damper 25 simultaneously according to the signal to the damper control motor 26 so as to regulate the amount of air supplied to a furnace 27 of the boiler from a blower 28 corresponding to the amount of the fuel oil supplied. Thereby steam pressure of a boiler will be maintained at a standard value at all times.

As described hereinabove, the ACC system which is provided on a boiler is designed for maintaining a steam pressure in the boiler at a constant value independently of the degree of opening of the turbine maneuvering valve, that is, the variation of the amount of steam supplied to the turbine. In a nutshell, this is nothing but a means for maintaining a balance between an amount of steam supplied to a turbine and that of fuel oil supplied to the boiler.

There appears to be no problem in the known prior art control system such as those described hereinabove as far as a theoretical matter is concerned. And hence, in general, this system is supposedly able to fulfill all above purposes sufficiently.

However, a prior art control system will show various disadvantages and inconveniences when it is actually used. For instance, when it is desired to have automatic control of a steam plant through a wide range of loads, several problems will arise as follows:

(1) Since a controllable range of an ACC system is approximately in the order of 10030% of the load, an automatic combustion control will be difficult at lower loads.

(2) Since a boiler operates slowly in response to any change, a follow-up capacity of the boiler pressure, in

' other words, the combustion within a boiler, will be insuflicient when the maneuvering handle for the turbine is positioned for an increased operating speed, resulting in an excessively high or low steam pressure of the boiler.

Accordingly, an operator must manipulate the manenuvering handle while watching the steam pressure of the boiler incessantly to prevent aforementioned occurrence.

(3) Since an applicable range of a single burner is in the order of IOU-15% of the load, even for special types, a plurality of burners must be lighted or cut out or some of the burners tips must be changed in case a boiler is operated in a range including an extremely low load. Such an operation has been carried out manually heretofore. However, if it is desired to carry out such an operation automatically by an ACC signal, the characteristics of the whole system should meet the requirements of the ACC system, resulting in a complex mechanism.

(4) Particularly in cases when it is desirable to control the marine steam power plant from the bridge, an operator must effect a control of the steam power plant simultaneously with that of the ship. However, it is actually diflicult to manipulate the steering wheel while watching the steam pressure in the boiler.

The present invention is contemplated for the purpose of eliminating afore-mentioned inconveniences and disadvantages inherent in prior art control systems and is characterized by the following points;

(1) Since the present invention consists of a system wherein ahead and astern running of a turbine, the amount of steam supplied to a turbine, the amount of fuel and air supplied to a boiler, including the number of burners in service, are directly controlled by a single maneuvering handle, the follow-up or response characteristics of the boiler will be considerably improved as compared with the prior art indirect control system in which amount of fuel is controlled by the boiler pressure.

(2) The amount of steam in a turbine and fuel and air consumption of the boiler will be set beforehand so that they may be substantially balanced in a steady running condition. A steady unbalanced condition existing tween both factors caused by an erroneous setting and a dyamical unbalanced condition mainly caused by a delay of energy transformation in the boiler will be corrected secondarily by an automatic boiler pressure control means.

(3) An automatic boiler pressure control means according to the present invention will correct either or both the degree of opening of the maneuvering valve, the fuel valve, and that of the air damper valve by a signal from a boiler pressure responsive means. A system, in which a degree of opening of the fuel valve Will be controlled by a signal from a boiler pressure responsive means, is known and adopted in prior art ACC systems. However, the signal from the boiler pressure responsive means will effect merely a secondary correction according to the present invention. Hence, an automatic boiler pressure control means may advantageously have a considerably small range of control according to the present invention as compared with the prior art control systems.

The resent invention will be described in detail by Way of examples according to two preferable embodiments hereinafter with reference to the accompanying drawings, wherein like reference numerals refer to like elements, in which:

FIG. 1 is a diagrammatic view showing a prior art control system for a marine steam power plant;

FIGS. 2 and 3 are diagrammatic views showing two different embodiments of control systems according to the present invention; and

FIG. 4 is a diagram showing the interrelation between the position of a maneuvering valve handle for the steam turbines, the degree of opening of a fuel valve and a maneuvering valve according to the present invention.

FIG. 2 shows an arrangement for carrying out the primary control of the boiler pressure by means of a maneuvering valve handle for the turbine. Referring to the drawing, when an operator manipulates a handle 14) of the turbine maneuvering valve to the ahead or astern position, the appropriate ahead or astern maneuvering valve 11 and 12, respectively will be opened by a signal coming through the wires 30 and 31, respectively, and simultaneously, :a fuel valve 21, an air damper 25, and a burner 23 will assume predetermined positions respectively corresponding to the degree of the opening of the actuated maneuvering valve 11 and 12 by a signal forwarded from a branchoif point 32 of the electric circuit through wires 33, 34, 35, and 36. Since an air ratio regulating means 37 is inserted between the wire 35 and air damper 25 and is responsive to the airflow sensor 38, a minute secondary regulation of air ratio will be carried out automatically.

A signal from the steam pressure sensor 29 will enter the automatic boiler pressure control means 19 through wire 20 and a pressure differential from a predetermined pressure, which is detected by said control means 19, will be forwarded to the appropriate maneuvering valve 11 or 12 in a form of signal through wires 30 and 31, re spectively, which will cause a secondary correction of the degree of opening of the maneuvering valve 11 or 12 which has been controlled primarily by the operation of the maneuvering valve handle for the turbine, so that the boiler pressure may be maintained at a predetermined value.

FIG. 3 shows one embodiment in which a secondary control of the boiler pressure is effected by a correction of degree of opening of the fuel valve or the air damper. The embodiment as illustrated in FIG. 3 differs from that of FIG. 2 only in an automatic boiler pressure control means 19, which is a kind of ACC system, and is identical with the latter in all other respects. Hence, merely a difference between those two systems will be described hereinafter.

The automatic boiler pressure control device 19 will send out signals commanding a correction for supplying the amount of fuel and air to the fuel valve 21 and the air damper 25, respectively, through wires 39 and 3d and through wires 40 and 35 based upon the amplitude of the boiler pressure sensor 29 signal entering therein through the circuit 20, and will correct secondarily the degree of opening of the fuel valve 21 and the air damper 25, which degree of opening has been controlled primarily by the turbine maneuvering handle 10.

FIG. 4 is a diagram wherein an interrelation between the position of the turbine maneuvering handle and the degree of opening of the fuel valve 21 that is, an amount of fuel supply and that of the ahead and astern maneuvering valve 11 and 12 according to the present invention is illustrated with the position of the handle along the abscissa and with the degree of opening of the fuel valve and the maneuvering valve along the ordinate, with a solid line F designating a variation curve of the degree of opening of the fuel valve and with a dotted line S designating a variation curve of the degree of opening of the maneuvering valves respectively.

As seen from the diagram, when a turbine maneuvering handle 10 is positioned in a neutral position 0, both the ahead and astern turbine maneuvering valves 11 and 12 will be closed and hence a steam supply to the turbines 13 and 14 will be cut off while the fuel valve 21 will be maintained open to a degree sufficient enough to supply minimum amount of fuel to the burner 23 merely for running a boiler furnace 27. If the turbine maneuvering handle 10 is moved to the right, in a direction of an arrowhead AHD, from a neutral position 0, both the degree F of opening of the fuel valve 21 and the degree S of opening of the ahead maneuvering valve 11 will be increased permitting the output of the ahead turbine 13 to be increased simultaneously. And if said turbine maneuvering handle 10 is moved to the left, in a direction of an arrowhead AST, from the neutral position 0, the degree F of opening of the fuel valve 21 will be increased in the same manner as in the case of an ahead command, and the degree S of opening of the astern maneuvering valve 12 will be increased with the ahead maneuvering valve 11 being closed, thus permitting the astern turbine 14 to be driven at a predetermined output.

As described hereinabove, the following advantages will be attained according to the present invention.

(1) Since an ahead and astern maneuvering valve and the fuel valve the air damper will be simultaneously and correspondingly actuated by means of a single turbine maneuvering handle, the boiler pressure control means may be of a size sufiicient to carry out a small amount of secondary adjustment, thus rendering a selection or construction of the automatic control means very easy. Accordingly, it is possible for a single operator to remotely control the plant through a Whole range of outputs by a single maneuvering handle.

(2) Since there will be no complicated requirements for the characteristics of the signal forwarded from the turbine maneuvering handle to a plurality of burners to light or cut them off progressively, a very simply mechanism will suffice. That is, even though there may be some discontinuous points in a supplied amount of fuel at the time of progressive igniting and extinguishing of burners, they will be accepted since they are corrected by the secondary control.

(3) Particularly, when an automatic boiler pressure control system having a turbine maneuvering valve of the embodiment in FIG. 2, an operator may operate the turbine maneuvering handle at any speed, regardless of the variation of the boiler pressure. Accordingly, it is very suitable for a bridge maneuvering system.

Although a system in which either or both the degree of opening of the turbine maneuvering valve and the fuel valve and the air valve is secondarily adjusted and controlled by a signal from the boiler pressure responsive means as described hereinbefore in the above-mentioned embodiments, it is possible to carry out a more perfect control by secondarily correcting both of them simultaneously, thus eliminating the slightest possible unbalance between a load of a turbine and that of a boiler.

The present invention has been described in connection with a particular structural embodiment which has proven satisfactory in use; however, it is appreciated that the structural embodiment may be modified without departing from the intended spirit and scope of the present invention as defined in the appended claims.

What is claimed is:

1. A device for controlling a marine steam power plant comprising a turbine, direction controlling turbine maneuvering valves, a fuel valve and air dampening valve for a boiler means, means for primarily controlling the degree of opening of said valves comprising a single maneuvering handle operatively connected to each said valve, said fuel valve being opened a minimum amount and said maneuvering valves being fully closed when said handle is in a neutral position, and secondary controlling means for controlling the degree of opening of said valves, comprising means responsive to an automatic boiler pressure control means which is actuated by a signal from a boiler pressure responsive means to eliminate an unbalance between the amount of fuel and air supplied to the boiler and the amount of steam supplied to the turbine.

2. An apparatus for controlling a marine steam power plant comprising a turbine, ahead and astern turbine maneuvering valves, a fuel valve and an air valve operatively connected to feed a boiler, a maneuvering handle, said handle being operative from a neutral position to positions for ahead and astern operation, said neutral position corresponding to a minimum degree of opening of said fuel valve and the fully closed position of said turbine maneuvering valves, the degree of opening of said fuel valve and said air valve and that of the selected direction maneuvering valve being primarily and simultaneously controlled in a correlated manner by moving said maneuvering handle in the direction of the desired movement, a means responsive to a signal from a boiler pressure responsive means for eliminating a possible unbalance between the amount of fuel supplied and air supplied to the boiler and the amount of steam supplied to the turbine by causing a secondary correction and control of the degree of opening of the turbine maneuvering valve.

3. An apparatus for the control of a marine steam power plant comprising an ahead turbine maneuvering valve, and astern turbine maneuvering valve, a fuel valve, an air valve, a direction maneuvering handle operatively connected to said valves, means responsive to the pressure in :a boiler, said direction maneuvering handle in a neutral position corresponding to a minimum opening of said fuel valve and the fully closed position of said turbine maneuvering valves, the degree of opening of said fuel valve, said air valve and the selected direction turbine maneuvering valve being primarily and simultaneously controlled in a correlated manner by an appropriate movement of said direction maneuvering handle, means to detect an unbalance between the amount of fuel supplied and air supplied to said boiler and the amount of steam supplied to said turbine, a secondary correction circuit controlling the degree of opening of the turbine maneuvering valve in response to a signal from said boiler pressure responsive means and said unbalance detector.

References Cited by the Examiner UNITED STATES PATENTS 2,580,345 12/1951 Dickey -102 2,598,235 5/1952 Dickey 60--l02 MARTIN P. SCHWADRON, Primary Examiner.

ROBERT R. BUNEVICH, Examiner. 

1. A DEVICE FOR CONTROLLING A MARINE STEAM POWER PLANT COMPRISING A TURBINE, DIRECTION CONTROLLING TURBINE MANEUVERING VALVES, FUEL VALVE AND AIR DAMPENING VALVE FOR A BOILER MEANS, MEANS FOR PRIMARILY CONTROLLING THE DEGREE OF OPENING OF SAID VALVES COMPRISING A SINGLE MANEUVERING HANDLE OPERATIVELY CONNECTED TO EACH SAID VALVE, SAID FUEL VALVE BEING OPENED A MINIMUM AMOUNT AND SAID MANEUVERING VALVES BEING FULLY CLOSED WHEN SAID HANDLE IS IN A NEUTRAL POSITION, AND SECONDARY CONTROLLING MEANS FOR CONTROLLING THE DEGREE OF OPENING OF SAID VALVES, COMPRISING MEANS RESPONSIVE TO AN AUTOMATIC BOILER PRESSURE CONTROL MEANS WHICH IS ACTUATED BY A SIGNAL FROM A BOILER PRESSURE RESPONSIVE MEANS TO ELIMINATE AN UNBALANCE BETWEEN THE AMOUNT OF FUEL AND AIR SUPPLIED TO THE BOILER AND THE AMOUNT OF STEAM SUPPLIED TO THE TURBINE. 